Precipitating tube bundle for wet electrofilters

ABSTRACT

A precipitation tube bundle for wet electrostatic filters is provided. The precipitation tube bundle consists of a plurality of single-piece precipitation tubes which are held at a distance from each other by an upper support collar, a central guide ring and a lower guide ring. The application is advantageous in that the tube bundle can be produced simply and economically, individual tubes can be replaced and when an electrical breakdown occurs in one of the precipitation tubes, the adjacent tubes are not damaged.

The invention relates to a precipitation tube bundle for wetelectrostatic filters, in particular for the precipitation of sulfuroxides and dust from exhaust gases. Filters of this kind consist of abundle of plastic tubes which are connected to each other at theirwalls. In the center of each tube there is an electrode. Duringoperation of the filter, the inner walls of the tubes are wetted with aflowing, electrically conductive washing fluid, and between theelectrode and the wall of the tube a strong electrical field isgenerated. This electrical field causes an ionization of the exhaustgases so that they are electrically charged and migrate to the walls ofthe tubes thereby following the lines of electric flux. At these wallsthe charged exhaust gas particles are taken up by the washing fluid andtransported to the outside via the ends of the tubes. In order to avoidelectrical breakdowns, the tubes are grounded.

DE-A1-41 02 732 discloses precipitation tube bundles in which theindividual tubes are bonded to each other on their external walls. It isa disadvantage of these precipitation tube bundles that individualprecipitation tubes cannot be replaced without being damaged and thatthe connection of the individual tubes requires much work and material.

In contrast thereto, it is an object of the present invention to providea precipitation tube bundle for wet electrostatic filters in which theindividual tubes can be held replaceably and in a low-stress and veryaccurate-to-dimension manner.

This object is achieved with the features of the claims.

In achieving this object, the invention starts out from the basic ideaof holding single-piece tubes in a form-fit connection by means of anupper support collar and a lower guide ring and, if necessary, a centralguide ring. By means of the support collar the bundle of tubes can besuspended in a housing. The lower guide ring serves for spacing thetubes apart and for connecting the tube grounding to the outside. Thecenter guide ring serves for spacing the tubes apart if the bundle oftubes is relatively long.

The invention has the following advantages.

By combining stable, low-stress and very accurate-to-dimension guide andsupport rings with the precipitation tubes, bundles of tubes having acontinuously smooth wall can be produced, wherein the distance betweenthe tubes is reduced to a minimum. Bundles of tubes of differentmaterials can be produced, for example, the supporting construction canbe made of a material different from that of the precipitation tubes.The precipitation tube bundles have tube walls being separated from eachother so that, for example, in case of voltage flashovers only therelevant tube is damaged. If they are damaged, the precipitation tubescan easily be replaced. Different kinds of grounding can easily beinserted in the precipitation tube bundles. The grounding can beprefabricated and easily be replaced or repaired in case of damage. Theprecipitation tube bundles can be produced more easily andcost-efficiently. In contrast to bundles consisting of connectedhalf-tube elements, in the present invention there are no splits and/orborderings.

In the following, the present invention will be explained in more detailin connection with the drawings, wherein the center electrode in thetubes has been omitted for reasons of simplification.

FIG. 1 shows a schematic side view of a precipitation tube bundleaccording to the invention in a housing,

FIG. 2 shows a cross-section along the line A—A in FIG. 1, and

FIG. 3 shows a cross-section along the line B—B in FIG. 1.

According to FIG. 1, a precipitation tube bundle 1 is suspended via asupporting flange 6 in a housing 7 on a projection 8. The smoke gases tobe filtered penetrate the tubes 2 in the axial direction parallel to theplane in the drawings. The upper portions of the tubes 2 are held by anupper support collar 3 being rigidly connected with the support flange6. The precipitation tube bundle 1 further comprises a center guide ring4 which is provided for spacing the tubes 2 apart. At the lower end theprecipitation tube bundle has a lower guide ring 5. The lower guide ring5 serves for spacing the tubes 2 apart and for connecting the tubegrounding to the outside. At the ends of the tubes the individual tubes2 have spot welding seams or shear welding seams which can alsopenetrate the walls of the tubes in order to secure the tubes in thesupport collar and/or the guide rings against an axial displacement. Thesupport collar 3 and the guide rings 4 and 5 hold the tubes in a formfit connection. The support flange 6 and the upper support collar 3 arepreferably welded on. Each tube 2 of the precipitation tube bundle 1 hasan upper grounding as an inner grounding and a lower grounding beingwelded into the surface of the tube and connected with the lower guidering 5. The groundings of the individual tubes 2 are electricallyconnected with each other.

FIG. 2 shows a cross-section along the line A—A through the uppersupport collar 3 in FIG. 1. The individual tubes are held by semi-tubeelements 3 a being connected with one another. In this way an exactdistance between the tubes can be guaranteed; thus, damage of adjacenttubes in case of electrical breakdowns is prevented and individual tubes2 can easily be replaced. The semi-tube elements 3 a are preferablyproduced of polypropylene in an injection molding process. Theprecipitation tubes 2 are produced in an extrusion process preferably ofpolypropylene or polyvinyl chloride or a conductive and/or hardlyinflammable thermoplastic material, wherein the inner wall of the tubeis preferably sand blasted in order to roughen the surface so that itcan more easily be wetted.

FIG. 3 shows a cross-section along the line B—B in FIG. 1. It can beseen that the tubes 2 are arranged in areas outside the upper supportcollar and the center and lower guide rings in a non-contacting manner.Thus, possibly occurring stresses can be compensated and there is a freespace for the replacement of, for example, damaged tubes 2. Preferably,the upper support collar 3 has a length of 900 mm in the axialdirection, and the center and lower guide rings 4, 5 each have a lengthof 300 mm. The inner grounding of each tube preferably consists of aninjection-molded ring made of polypropylene and comprising four graphiteinserts and a graphite sheet cover. The lower grounding of each tubepreferably consists of a carbon twine or flexible carbon tube.

The embodiment of the invention as shown in the drawings consists ofsingle-piece round tubes having a circular cross-section. Theprecipitation tube bundle can, however, also consist of single-piecehoneycomb tubes having a hexagonal cross-section.

What is claimed is:
 1. A precipitation tube bundle (1) for wetelectrostatic filters comprising (a) a plurality of single-pieceprecipitation tubes (2), (b) an upper support collar (3) for theprecipitation tubes (2), (c) an insert for grounding each of the tubes,said insert comprising an upper grounding as an inner grounding and alower grounding welded into a surface of the precipitation tube (2),wherein the groundings of the individual tubes (2) are electricallyconnected to each other, and wherein the inner grounding consists of aninjection-molded polypropylene ring and comprising four granite insertsand a graphite sheet cover and the lower grounding consists of a carbontwine or flexible carbon tube, and (d) a lower guide ring (5) forspacing the precipitation tubes (2) apart and for connecting the tubegrounding to the outside.
 2. The precipitation tube bundle according toclaim 1, characterized by at least one further guide ring (4) comprisinga center guide ring being arranged between the upper support collar (3)and the lower guide ring (5) and serving for spacing the precipitationtubes (2) apart.
 3. The precipitation tube bundle according to claim 1,characterized in that the precipitation tubes (2) are produced byextrusion.
 4. The precipitation tube bundle according to claim 1,characterized in that on inner surfaces of the precipitation tubes (2)are sand blasted.
 5. The precipitation tube bundle according to claim 1,characterized in that tube ends of the precipitation tubes (2) have spotwelding seams or shear welding seams in order to axially secure thetubes.
 6. The precipitation tube bundle according to claim 5,characterized in that the welding seams penetrate a wall of the tube. 7.The precipitation tube bundle according to claim 2, characterized inthat the upper support collar (3), the center guide ring (4) and thelower guide ring (5) hold the precipitation tubes (2) in a form-fitconnection.
 8. The precipitation tube bundle according to claim 1,characterized in that the upper support collar (3) comprises a supportring (6) for supporting the precipitation tube bundle (1) in a housing(7).
 9. The precipitation tube bundle according to claim 8,characterized in that the support ring (6) is welded to the supportcollar.
 10. The precipitation tube bundle according to claim 1,characterized in that the upper support collar (3), the center guidering (4) and the lower guide ring (5) each consist of semi-tube elements(3 a) which are connected with each other.
 11. The precipitation tubebundle according to claim 10, characterized in that the semi-tubeelements (3 a) are produced by injection molding.
 12. The precipitationtube bundle according to claim 2, characterized in that the uppersupport collar (3), the center guide ring (4) and the lower guide ring(5) are made of polypropylene.
 13. The precipitation tube bundleaccording to claim 1, characterized in that the precipitation tubes (2)are made of polypropylene or polyvinyl chloride or a conductive and/orhardly inflammable plastic material (thermoplastic material).
 14. Theprecipitation tube bundle according to claim 2, characterized in that inan axial direction the upper support collar (3) is 900 mm long and thecenter guide ring (4) and the lower guide ring (5) are each 300 mm long.15. The precipitation tube bundle according to claim 1, characterized inthat the precipitation tubes (2) are round tubes or honeycomb tubes.